(IANAL) A chargeback is literally declaring a credit card fraud. It's a very good and very necessary consumer protection, but it is very expensive to the vendor for ambiguous "there's no proof either way", which is where it can be abused. It's also a last resort for cases where the vendor acted fraudulently, or your credit card was stolen or cloned. Anyone who owns a credit card should know that.
I asked for a chargeback a couple times but it was real fraud, and my card was cloned. When you ask a chargeback, you are recorded on the phone for your statements for their investigation.You need to say that you never made that purchase, that you do not have an account with that company, and they also ask if it's possible at all that a family member could have made the purchase. They ask you to be sure it's not just because you don't remember. They repeat it's a very serious action. If you do have an account they ask you to resolving the charges with the vendor first.